Maitrise de la fermentation butyrique par la microflore lactique réductrice

Clostridium tyrobutyricum, bactérie anaérobie stricte, endosporulée, est à l’origine de l’apparition du défaut appelé «gonflement tardif » lors de l’étape d’affinage de nombreux fromages à pâtes pressées non cuites et cuites. Selon d’Incecco et al. (2018), elle passerait de l’état spore à un état de cellule végétative à la fin de l’étape d’acidification. Par ailleurs dans le projet ANR FoodREDOX, il a été montré qu’un ensemencement dans le lait d’une microflore abaissant le potentiel d’oxydoréduction, ralentirait la consommation de lactates et la production de butyrate par C. tyrobutyricum lors de l’affinage des fromages. Ainsi, connaître et comprendre les mécanismes de germination, sporula…

Identification and expression of Lactobacillus paracasei genes for adaptation to desiccation and rehydration

AbstractLactobacillus paracaseiis able to persist in a variety of natural and technological environments despite physico-chemical perturbations, in particular alternations between desiccation and rehydration. However, the way in which it adapts to hydric fluctuations and in particular the genetic determinants involved are not clearly understood. To identify the genes involved in adaptation to desiccation, an annotated library ofL. paracaseirandom transposon mutants was screened for viability after desiccation (25% relative humidity, 25°C). Subsequently, the expression of the identified genes was measured at five stages of the dehydration-rehydration process to formulate the chronology of ge…

Screening of lactic acid bacteria based on their reduction kinetics

Lactic Acid bacteria (LAB) are widespread in the dairy industry for their use as starters and probiotics. They are able to reduce redox potential (E h) of food matrices, influencing oxidation-reduction reactions involved in the organoleptic quality of the product and also preventing the development of undesired microflora. Amongst LAB, some species are able to reduce E h below negative values while others do not [1]. This diversity of reducing activity found in LAB allows the use of selected strains providing optimal reduction values necessary to the overall quality of food dairy products. Currently, there are different ways to compare LAB based on their reducing properties. Cachon et al., …

Screening of Lactococcus lactis starters with Absorbance Reduction Activity Method (ARAm)

Lactococcus lactis is one of the most used species in the dairy industry. This species has the ability to reduce to very negative values the redox potential (Eh) of food matrices, making it one of the most reducing Lactic Acid Bacteria (LAB) [1]. This reducing activity influences oxidation-reduction reactions involved in the organoleptic quality of the product and prevents the undesired microorganisms development [2–4]. The main mechanism involved are exofacial thiol groups, NoxE NADH Oxidase and the Electron Transport Chain mechanism [5-7]. For Eh measurement, the commonly used method consists of a redox probe placed in a liquid medium or food matrix [8]. With this probe, Cachon et al. (20…

[Thu-P1-055] Influence of fermented food consumption on taste and oral microbiota of rats

Oral microbiota varies throughout the individual’s life. These changes are due to several factors (environmental, physiological, lifestyle...) that shape its diversity and composition. However, little is known about the physiological impact of this persistence. Taste perception is one of the possible targeted functions. Indeed, our team has recently established relationships between oral microbiota and taste sensitivity in humans. The objective of this work was to see if fermented food bacteria were able to persist in the oral cavity and consequently influence the oral microbiota and the taste by using a rodent experimental design: two groups of rats (n=27/group) were fed for 3 weeks with e…

Identification and transcriptional profile of Lactobacillus paracasei genes involved in the response to desiccation and rehydration

International audience; Lactobacillus paracasei is able to persist in a variety of natural and technological environments despite physico-chemical perturbations, in particular alternations between desiccation and rehydration. However, the way in which it adapts to hydric fluctuations and the genetic determinants involved are not clearly understood. To identify the genes involved in adaptation to desiccation, an annotated library of L. paracasei random transposon mutants was screened for viability after desiccation (25% relative humidity, 25 °C). We found 16 genes that have not been described as being involved in this response. Most of them are linked to either the transport of molecules or …

[Thu-P1-056] Is taste linked to oral microbiota?

Taste perception varies strongly between individuals but the factors at the origin of this variability are not fully understood. For example, different events occurring at the vicinity of the taste receptors on the tongue can modulate taste perception. Our group has recently suggested that the microbiota at the surface of the tongue could be involved by controlling the taste compounds concentration in the lingual film (the biological material covering the tongue). The aim of this work is to evaluate the contribution of the oral microbiota to taste. To do this, taste sensitivity (5 basic tastes) was determined in 100 healthy adult subjects and the microbiota of their lingual film and saliva …

Functional genomics of Lactobacillus casei establishment in the gut

International audience; Although the composition of the gut microbiota and its symbiotic contribution to key host physiological functions are well established, little is known as yet about the bacterial factors that account for this symbiosis. We selected Lactobacillus casei as a model microorganism to proceed to genomewide identification of the functions required for a symbiont to establish colonization in the gut. As a result of our recent development of a transposon-mutagenesis tool that overcomes the barrier that had prevented L. casei random mutagenesis, we developed a signature-tagged mutagenesis approach combining whole-genome reverse genetics using a set of tagged transposons and in…

Study of the cwaRS-ldcA Operon Coding a Two-Component System and a Putative L,D-Carboxypeptidase in Lactobacillus paracasei

International audience; The cell surface is the primary recognition site between the bacterium and the host. An operon of three genes, LSEI_0219 (cwaR), LSEI_0220 (cwaS), and LSEI_0221 (ldcA), has been previously identified as required for the establishment of Lactobacillus paracasei in the gut. The genes cwaR and cwaS encode a predicted two-component system (TCS) and ldcA a predicted D-alanyl-D-alanine carboxypeptidase which is a peptidoglycan (PG) biosynthesis enzyme. We explored the functionality and the physiological role of these three genes, particularly their impact on the bacterial cell wall architecture and on the bacterial adaptation to environmental perturbations in the gut. The …

Rapid 96-well plates DNA extraction and sequencing procedures to identify genome-wide transposon insertion sites in a difficult to lyse bacterium: Lactobacillus casei

International audience; Random transposon mutagenesis followed by adequate screening methods is an unavoidable procedure to characterize genetics of bacterial adaptation to environmental changes. We have recently constructed a mutant library of Lactobacillus casei and we aimed to fully annotate it. However, we have observed that, for L. casei which is a difficult to lyse bacterium, methods used to identify the transposon insertion site in a few mutants (transposon rescue by restriction and recircularization or PCR-based methods) were not transposable for a larger number because they are too time-consuming and sometimes not reliable. Here, we describe a method for large-scale and reliable id…

Kinetics and Intensity of the Expression of Genes Involved in the Stress Response Tightly Induced by Phenolic Acids in <i>Lactobacillus plantarum</i>

In <i>Lactobacillus plantarum</i>, PadR, the negative transcriptional regulator of <i>padA </i>encoding the phenolic acid decarboxylase, is divergently oriented from <i>padA. </i>Moreover, it forms an operonic structure with <i>usp1,</i> a genewhose products display homology with proteins belonging to the UspA family of universal stress proteins. PadR is inactivated by the addition of <i>p-</i>coumaric, ferulic or caffeic acid to the culture medium. In order to better characterize the stress response of this bacterium to phenolic acids, we report here the kinetics and quantitative expression by qRT-PCR of the 3 genes from the <i…

Does the lingual film intervene in the perception of taste?

International audience; The biological film at the surface of the tongue, composed of saliva and microorganims, is an important interface between exogenous taste molecules and receptors involved in taste perception. However, the relationships between the composition of the lingual film and the perception of taste are not fully described. Thus, the aim of the present work was to study the differences in the biochemical (protein concentration, metabolite profiles) and microbiological compositions of the tongue films from 20 adult subjects, and to explore the possible relationships between composition and taste sensitivity assessed by means of a rapid at-home test. Preliminary results showed t…

New Genes Involved in Mild Stress Response Identified by Transposon Mutagenesis in Lactobacillus paracasei

International audience; Lactic acid bacteria (LAB) are associated with various plant, animal, and human niches and are also present in many fermented foods and beverages. Thus, they are subjected to several stress conditions and have developed advanced response mechanisms to resist, adapt, and grow. This work aimed to identify the genes involved in some stress adaptation mechanisms in LAB. For this purpose, global reverse genetics was applied by screening a library of 1287 Lactobacillus paracasei transposon mutants for mild monofactorial stresses. This library was submitted independently to heat (52 degrees C, 30 min), ethanol (170 g.L-1, 30 min), salt (NaCl 0.8 M, 24 h), acid (pH 4.5, 24 h…

Oral microbiota modulation by fermented food; impact of salivary proteome

International audience

Is oral microbiota implicated in taste? A shotgun metagenomics approach

Criblage des bactéries lactiques en fonction de leur cinétique de réduction : approche méthodologique

Les bactéries lactiques (BL) sont des micro-organismes importants dans l'industrie alimentaire pour la fabrication de produits fermentés ou comme probiotiques. Parmi les BL, certaines espèces sont capables de réduire le potentiel d’oxydoréduction (Eh) jusqu’à des valeurs négatives alors que d'autres non [1]. Cette diversité d'activité réductrice retrouvée chez les BL permet l'utilisation de souches sélectionnées apportant des valeurs de réduction optimales nécessaires à la qualité globale des produits laitiers [2–6]. Les principaux mécanismes impliqués sont les groupes thiol exofaciaux, la NoxE NADH Oxydase et le mécanisme mettant en jeu la chaîne de transport d'électrons [7,8,9].Actuelleme…

Is oral microbiota linked to taste perception in human?

Development of an Efficient In Vivo System (P-junc-TpaseIS(1223)) for Random Transposon Mutagenesis of Lactobacillus casei

ABSTRACT The random transposon mutagenesis system P junc -TpaseIS 1223 is composed of plasmids pVI129, expressing IS 1223 transposase, and pVI110, a suicide transposon plasmid carrying the P junc sequence, the substrate of the IS 1223 transposase. This system is particularly efficient in Lactobacillus casei , as more than 10,000 stable, random mutants were routinely obtained via electroporation.

Fermentation Products of Commensal Bacteria Alter Enterocyte Lipid Metabolism

eferred to byJia Wen, John F. RawlsFeeling the Burn: Intestinal Epithelial Cells Modify Their Lipid Metabolism in Response to Bacterial Fermentation ProductsCell Host & Microbe, Volume 27, Issue 3, 11 March 2020, Pages 314-316; International audience; Despite the recognized capacity of the gut microbiota to regulate intestinal lipid metabolism, the role of specific commensal species remains undefined. Here, we aimed to understand the bacterial effectors and molecular mechanisms by which Lactobacillus paracasei and Escherichia coli regulate lipid metabolism in enterocytes. We show that L-lactate produced by L. paracasei inhibits chylomicron secretion from enterocytes and promotes lipid stora…